People care when they have paid you to optimize their site but they only get a score 86/100.

Trying to explain the page speed tool is just a 'rough guide' and that a website always has to be some kind of compromise between speed, functionality and design falls on deaf ears because 'google' is, well, 'google'.

I agree but like everything with optimization and refactoring, the cost to move up towards a 100 offers less ROI in the end. I think if you're at 90 that's solid, no desire to be in the 100 club nor would I tell a client you need to be there.

90 for mobile, desktop, both?

I was at a top 1000 site and the senior product manager offered free dinner to be the first team to hit certain metrics (like pagespeed). He knew 100/100 wasn't useful but the difference between 50 and 90 for us was fairly significant. Are you chasing a number or what the number means? The latter is a good thing.

Yea my casual survey/experience indicates optimizing beyond high 80s isn't going to affect search ranking much. I'm obsessive about optimizing page speed too, but maxing out their score requires some gimmicky (imo) techniques that don't really affect speed/ux.